water.  Monitor  BRAKE  DEICE  ON  ammunciator  for  auto- matic   termination   of   system   operation   and   then   turn   the switch   OFF.   During   flight,   trim   tabs   and   controls   should also   be   exercised   periodically   to   prevent   freeing.   Ensure that   anti-icing   systems   are   activated   before   entering   icing conditions.   Do   not   activate   the   surface   deice   system   until ice  has  accumulated  at  least  0.5  INCH  The  propeller  deice system   operates   effectively   as   an   anti-ice   system   and   it may  be  operated  continuously  in  flight  If  propeller  imbal- ance  due  to  ice  does  occur,  it  may  be  relieved  by  increas- ing  RPM  briefly,  then  returning  to  desired  setting. Ice   vanes   must   be   extended   when   opening   in   visible moisture  or  when  freedom  from  visible  moisture  cannot  be assured,  at  +5°C  FAT  or  less.  Ice  vanes  are  designed  as  an anti-ice   system,   not   a   deice   system.   After   the   engine   air inlet  screens  are  blocked,  lowering  the  ice  vanes  will  not rectify   the   condition (2)    Stalling   airspeeds   should   be   expected   to increase  when  ice  has  accumulated  on  the  aircraft  causing distortion   of   the   wing   airfoil.   For   the   same   reason,   stall warning  devices  are  not  accurate  and  should  not  be  relied upon.   Keep   a   comfortable   margin   of   airspeed   above   the normal  stall  airspeed.  Maintain  a  minimum  of  140  KNOTS during  sustained  icing  conditions  to  prevent  ice  accumula- tion   on   unprotected   surfaces   of   the   wing.   In   the   event   of windshield  icing,  reduce  airspeed  to  226  KNOTS  or  below. h.    Descent.    Use   normal   procedures   in   Section   II. Brake   deicing   should   be   considered   if   moisture   was encountered  during  previous  ground  operations  or  in  flight, in  icing  conditions  with  gear  extended. i.   Landing.   Landing   on   an   icy   runway   should   be attempted   only   when   absolutely   necessary   and   should   not be  attempted  unless  the  wind  is  within  10°  of  runway  head- ing.  Application  of  brakes  without  skidding  the  tires  on  ice is  very  difficult,  due  to  the  sensitive  brakes.  In  order  not  to impair   pilot   visibility,   reverse   thrust   should   be   used   with caution  when  landing  on  a  runway  covered  with  snow  or standing   water.   Use   procedures   in   Section   II   for   normal landing. j.    Engine    Shutdown.    Use   normal   procedures   in   Sec- tion II. k.   Before   Leaving   Aircraft.   When   the   aircraft   is parked  outside  on  ice  or  in  a  fluctuating  freeze-thaw  tem- perature  condition  the  following  procedures  should  be  fol- lowed  in  addition  to  the  normal  procedures  in  Section  II. After  wheel  chocks  are  in  place,  release  the  brakes  to  pre- vent   freezing.   Fill   fuel   tanks   to   minimize   condensation, remove  any  accumulation  of  dirt  and  ice  from  the  landing TM   1-1510-223-10 gear   shock   struts,   and   install   protective   covers   to   guard against  possible  collection  of  snow  and  ice. 8-49.  DESERT  OPERATION  AND  HOT  WEATHER OPERATION. Dust,   sand,   and   high   temperatures   encountered   during desert  operation  can  sharply  reduce  the  operational  life  of the  aircraft  and  its  equipment  The  abrasive  characteristics of  dust  and  sand  upon  turbine  blades  and  moving  parts  of the  aircraft  and  the  destructive  effect  of  heat  upon  the  air- craft   instruments   will   necessitate   many   hours   of   mainte- nance   if   basic   preventive   measures   are   not   followed   In flight,   the   hazards   of   dust   and   sand   will   be   difficult   to escape,  since  dust  clouds  over  a  desert  may  be  found  at altitudes  up  to  10,000  feet  During  hot  weather  operations, the  principal  difficulties  encountered  are  high  turbine  gas temperatures  (TGT)  during  engine  starting,  over-heating  of brakes,  and  longer  takeoff  and  landing  distances  due  to  the higher   density   altitudes   encountered   In   areas   where   high humidity   is   encountered,   electrical   equipment   (such   as communication  equipment  and  instruments)  will  be  subject to   malfunction   by   corrosion   fungi,   and   moisture   absorp- tion  by  nonmetallic  materials. a.   Preparation   For   Flight.   Check  the  position  of  the aircraft   in   relation   to   other   aircraft   Propeller   blown   sand can   damage   nearby   aircraft   Check   that   the   landing   gear shock  struts  are  free  of  dust  and  sand.  Check  instrument panel  and  general  interior  for  dust  and  sand  accumulation Open  main  entrance  door  and  cockpit  vent  storm  windows to  ventilate  the  aircraft b.   Engine   Starting.   Use  normal  procedures  in  Section IL  Engine  starting  under  conditions  of  high  ambient  tem- peratures  may  produce  a  higher  than  normal  TGT  during the  start.  The  TGT  should  be  closely  monitored  when  the CONDITION  lever  is  moved  to  the  LOW  IDLE  position If   overtemperature   tendencies   are   encountered,   the   CON- DITION lever should be moved to IDLE CUTOFF position periodically   during   acceleration   of   gas   generator   RPM (N ₁ ). Be prepared to abort the start before temperature lim- itations  are  exceeded. c.    Warm-Up    Ground    Tests.    Use   normal   procedures in  Section  II. d.   Taxing.   Use   normal   procedures   in   Section   II. When  practical,  avoid  taxiing  over  sandy  terrain  to  mini- mize  propeller  damage  and  engine  deterioration  that  results from  impingement  of  sand  and  gravel.  During  hot  weather operation,   use   minimum   braking   action   to   prevent   brake overheating. e.    Takeoff.    Use   normal   procedures   in   Section   II. Avoid  taking  off  in  the  wake  of  another  aircraft  if  the  nut- way  surface  is  sandy  or  dusty. 8-31